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Phases of a Clinical Trial

Topic Overview

A clinical trial is done to find out if a medicine or treatment
is safe and works well for treating a certain condition or
disease.

A
medicine or treatment must go through three phases before it is
approved for use by the U.S. Food and Drug Administration (FDA). A fourth phase happens after the medicine or treatment has been approved.

Phase I: A new medicine is tested for the first
time on a small group of healthy people or people with certain conditions or
diseases. Researchers check the safety of the medicine or treatment, the
best dose or schedule to use, and what types of side effects occur. During this
phase, all the people involved in the study (patients, doctors, and
researchers) know what medicine is being used. These are called nonrandomized,
nonblinded studies.

Phase II: The medicine or treatment is tested on
a larger group of people with certain conditions or diseases. This phase helps
researchers find out how well a medicine or treatment will work to treat
a particular problem. Phase II trials are also usually nonrandomized,
nonblinded studies.

Phase III: The medicine or treatment is
tested on even larger groups. The medicine is studied to find out how well it
works compared with standard treatment or placebo. Researchers also study whether the medicine improves
specific areas in your life, such as how well you are able to keep your
usual routine. Most medicines that reach this phase will be considered
for FDA approval. During phase III trials, participants receive the study
medicine, a placebo, or the standard treatment. Neither the participants, the
doctors, nor the researchers know which person is getting which medicine. These
are called randomized and double-blinded studies.

Phase IV: Medicines are
also studied after they are approved. These studies can find new uses for the medicine,
different ways to give it, or more safety information. For example,
a medicine may be studied to see how well it works for a certain population,
such as adults over the age of 65 or a certain racial group.

New combinations of approved medicines can
be studied in phase II, phase III, or phase IV trials.

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